BRAKE PAD WITH OPTIMISED COOLING

Abstract

The invention concerns a brake pad (10) for a disc brake caliper, the pad (10) comprising a support plate (11). According to the invention, the support plate (11) has cooling fins (17), thus creating a convection zone (16).

Claims

1. Brake pad (10) for a disc brake caliper (20), the pad (10) comprising a support plate (11), characterized in that the support plate (11) has cooling fins (17), thus creating a convection zone (16).

2. Brake pad (10) according to claim 1, characterized in that the support plate (11) has a rear face (12) with a contact zone (12a), the contact zone (12a) is thermally insulated from other caliper components (20) by a thermal insulator (13), and the thermal insulator (13) covers only part of the rear face (12), leaving an uncovered rear zone (12b), which is also part of the convection zone (16).

3. Brake pad (10) according to any of the preceding claims, characterized in that the support plate (11) has a front face (14) receiving a lining (15) with a friction zone, and the lining (15) covers only part of the front face (14), leaving an uncovered front zone (14b), which is also part of the convection zone (16).

4. Brake pad (10) according to claim 2, characterized in that the uncovered rear zone (12b) represents at least 10% of the rear face area (12), preferably at least 20%.

5. Brake pad (10) according to any of the preceding claims, characterized in that the convection zone (16) is located on either side of the pad (10).

6. Brake pad (10) according to any of the preceding claims, characterized in that the support plate (11) is made of low-alloy steel, comprising less than 0.3% by mass of carbon, preferably less than 0.2%, and vanadium in an amount between 0.2 and 0.3% by mass.

7. Brake pad (10) according to claim 1, characterized in that the support plate (11) has a rear face (12) with a contact zone (12a), the contact zone (12a) is thermally insulated from other caliper components (20) by a thermal insulator (13) in the form of a sheet.

8. Brake pad (10) according to claim 7, characterized in that the insulator (13) is held by a clip (18) snapped onto the support plate (11).

9. Brake pad (10) according to claim 8, characterized in that the clip (18) is made of austenitic steel.

10. Brake pad (10) according to claim 2 or claim 7, characterized in that the insulator (13) comprises mica.

11. Caliper (20) for a disc brake equipped with a break pad (10) according to any of the preceding claims.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] FIG. 1 is a rear perspective view of a support plate of a brake pad according to the invention.

[0032] FIG. 2 is a rear perspective view of another brake pad support plate according to the invention.

[0033] FIG. 3 is a rear perspective view of such a pad.

[0034] FIG. 4 is a front view of the support plate.

[0035] FIG. 5 is a partial front view of a caliper according to the invention.

[0036] FIG. 6 is a perspective view of such a caliper.

DETAILED DESCRIPTION OF THE INVENTION

[0037] With reference to FIGS. 1 to 6, the invention essentially consists of designing, for a brake pad (10), an arrangement of the thermal insulator (13) such that at least one uncovered rear zone (12b) is visible, meaning it is not covered by the thermal insulator (13).

[0038] It is recalled that this insulator (13) is necessary to protect other components of the caliper (20) from heat, but limiting its presence to the strictly necessary, that is, to the contact zone (12a) only (the interface between the rear face (12) and the parts applying the clamping force) allows creating at least one convection zone (16) for evacuating the heat generated during braking.

[0039] The thermal insulator (13) advantageously comprises mica, providing an effective insulator even with a small thickness. The mica sheet is held in position on the plate (11) by a clip (18), which is snapped onto the plate (11).

[0040] In practice, it is advantageous to design a support plate (11) that is oversized, meaning it is wider than required by the dimensions of the lining (15) and the contact zone (12a).

[0041] FIGS. 1, 2, and 4 show the outlines corresponding to the dimensions of the lining (15) on the front face (14) and the contact zone (12a) on the rear face (12). A sufficient size for the support plate (11) is the smallest geometry that encompasses these outlines, as illustrated in FIG. 1.

[0042] With reference to FIGS. 2 and 4, the plate (11) is oversized so that: [0043] On the rear face (12), significant portions extend beyond the insulator (13), forming large uncovered rear zones (12b); [0044] On the front face (14), significant portions extend beyond the lining (15), forming large uncovered front zones (14b).

[0045] This significantly increases the surface area of the convection zone (16), which linearly increases the energy that can be dissipated by this zone (16).

[0046] We are not specifically concerned with the functional surfaces for connecting the plate (11) to the caliper (20), which are not covered by the insulator (13) or the lining (14), as the invention mainly lies in the addition of fins (17) and preferably the additional addition of uncovered rear zones (12b) and uncovered front zones (14b).

[0047] There is generally space available on the sides of a pad (10) for such oversizing. Of course, increasing the thickness of the plate (11) is not considered since its edge, although participating in thermal exchanges by convection, would not yield significant gains by increasing the thickness. Furthermore, space in this direction is limited.

[0048] The surface area of the uncovered rear zone (12b) represents at least 10% of the rear face area (12), preferably at least 20%. In the illustrated mode, the surface area of the uncovered rear zone (12b) represents about 40% of the rear face area (12).

[0049] If the lining (15) does not cover the entire front face (14), the surface area of the uncovered front zone (14b) represents at least 10% of the front face area (14), preferably at least 20%. In the illustrated mode, the surface area of the uncovered front zone (14b) represents about 30% of the front face area (14).

[0050] These ratios ensure that the convection zone (16) is large enough to evacuate the heat generated during braking.

[0051] To evacuate heat more easily, it is advantageous not to place the convection zone (16) on only one side of the plate (11), but rather on both sides. In the illustrated embodiments, the convection zone (16) is positioned on the right and left. Depending on the available space, it is also possible to extend the convection zone (16) upwards and downwards.

[0052] The pad (10) thus designed can withstand very high braking efforts, generating a large amount of heat, and then dissipate this heat quickly. It is therefore important that the material constituting it is suitable to withstand such thermal constraints, which are deleterious due to: [0053] The temperature values reached (sometimes exceeding 700 C.), and [0054] The frequency of braking (typically 5 to 10 braking events per minute during motorsports use).

[0055] A material suitable for meeting such thermal and mechanical constraints is the 15CDV6 steel alloy.

[0056] Tests were conducted by the Applicant comparing 15CDV6 steel with a steel known as Imex700 or S 690 QL according to the European standard EN 10025-6: March 2005, initially used to make the plate (11) and the 15CDV6.

[0057] The tests consisted of bending tests on Imex700 specimens and 15CDV6 specimens. The specimens have identical dimensions, except for the thickness of 4 mm for Imex700 and 3 mm for 15CDV6. During the bending test, the specimen is held horizontally and fixedly at one end by a clamp, and a weight is suspended from the other end. A section of the specimen near the clamp is reduced to ensure the specimen bends at that point. The distance between the free end of the specimen and the reduced section is 150 mm.

[0058] The specimen is first tested at 21 C. by suspending weights until plastic deformation of the reduced section occurs.

[0059] Then, a new specimen is tested by suspending weights and heating the reduced section to 600 C. The specimen is then allowed to cool in air, and its straightness is checked to determine if the elastic limit has been exceeded. Tests are repeated with different weights until the limit between elastic and plastic deformation is found.

[0060] The test results are compiled in the table below, noting that given the difference in thickness between the specimens, the induced stress was normalized to account for this difference.

TABLE-US-00001 TABLE 1 Bending Induced Thickness Weight Stress Steel (mm) (kg) (Mpa) Bent Heated 15CDV6 3 14.06 1970 Yes 21 C. 15CDV6 3 7.02 984 Yes 600 C. 15CDV6 3 5.6 785 No 600 C. Imex700 4 17 1340 Yes 21 C. Imex700 4 8.62 680 Yes 600 C. Imex700 4 5.82 459 No 600 C.

[0061] It can be seen that 15CDV6 withstands an induced stress of 785 Mpa when heated to 600 C., while Imex 700 withstands only 459 Mpa. Thus, 15CDV6 is 70% more resistant than Imex700.

[0062] Since the pad (10) is designed to withstand very high braking efforts, it is necessary to reinforce the zones ensuring its kinematic connection with the caliper (20). In this case, a kinematic connection of the slider type is obtained by hemispherical ears present on the plate (11) cooperating with sleeves (21) of the caliper (20). However, the direction of significant braking is always the same, that of the vehicle's advance: it is, therefore, not judicious to reinforce the connection on both sides of the pad (10).

[0063] The pad (10) is, in the illustrated mode, asymmetrical: only one reinforced portion (19) is present, arranged to retain the pad (10) in the braking direction (DF) illustrated in FIG. 5.

[0064] Since the pads (10) are asymmetrical, they must not be mounted upside down on the caliper (20). Anti-mistake means are, therefore, present. With reference to FIG. 6, it could be, for example, a stop (22) mounted on the caliper (20), and the reinforced portion (19) is configured to stop against the stop (22). Therefore, it is not possible to mount the pad (10) upside down.

[0065] The pads (10) according to the invention exhibit excellent thermal performance, maintaining the caliper (20) temperature at only 60 C. while braking efforts have led the disc (40) to a temperature of around 800 C. (the metal of the disc (40) is red-hot).

[0066] Nevertheless, the pads (10) have very limited bulk, especially in terms of thickness. Moreover, a too large thickness tends to tip the pads during braking. A thin pad also helps limit uneven wear.

[0067] Additionally, the pad (10) and the caliper (20) can be shaped differently from the given examples without departing from the scope of the invention, defined by the claims.

[0068] Furthermore, the technical characteristics of the different embodiments and variants mentioned above can be combined, in whole or in part. Thus, the pad (10) and the caliper (20) can be adapted in terms of cost, functionality, and performance.